Separation of fluid catalytic cracking equilibrium catalysts to improve value and reduce waste

ABSTRACT

Useful portions of equilibrium catalyst from a Fluid Catalytic Cracking unit are obtained by fractionating to obtain a narrow size fraction, followed by separation of the narrow size fraction using density as a fractionating criterion. Size fractionating may be performed in vibrating sieves, and the density fractionating may be performed in an air cyclone. Both beneficial and detrimental fractions can be identified; in one embodiment, large particles are removed from ECAT to improve the coking factor.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/216,421 filed May 18, 2009 and U.S. Provisional Application No.61/278,735 filed Oct. 13, 2009 which are both incorporated by referencein their entireties.

TECHNICAL FIELD

Equilibrium catalysts (ECAT) are separated by air classifying, sievingand air cyclone steps into size and density fractions qualifying forreuse as equilibrium catalysts, such as particulate fractions relativelypoor in nickel or vanadium.

BACKGROUND OF THE INVENTION

The Fluid Catalytic Cracking process unit (“FCC unit”) is one of themost important upgrading processes in a refinery. In the FCC unit, solidparticulate catalyst makes intimate contact with vaporized or gaseoushydrocarbons in a column, forming a fluidized bed having temperaturescontrolled to effect the desired cracking of the larger hydrocarbonmolecules.

The physical properties of the catalysts used in FCC units, “FCCCatalysts” are designed such that even though the catalyst is a solid,it behaves like a liquid when enough fluidizing media (i.e. vapors, air)are present. In general, the average particle size of a FCC catalystparticle is between 60 and 90 microns. Two important parameters are thepercent by weight of the total below 20 microns and the percent byweight of the total below 40 microns. The first parameter is importantas an indication of losses or potential losses, as the cyclonic systemsused in FCC units are generally designed with a cutoff in efficiency ataround 20 microns, and particles below 20 microns are more difficult toprevent from releasing to the atmosphere and therefore more likely topresent an environmental problem. The losses can be detrimental botheconomically and environmentally. Cyclonic systems or cyclones and airseparators are well known devices used to separate materials ofdifferent physical properties. In particular, cyclones can separatemixtures of solids with different particle size, density, relative massor any combination thereof. Anything below 20 microns is lost veryrapidly from the air cyclone process and is either captured by higherefficiency systems downstream or emitted to the atmosphere. The 0-40micron content is important as particles in the 20-40 micron regime areimportant for fluidization in the system. Poor fluidization stemmingfrom a relatively low component of smaller particles can result inreduced catalyst circulation or fluid bed instability.

Another particular characteristic of the FCC process is that in order tomaintain the proper level of catalyst and the correct activity andselectivity of the system, a certain percentage of catalyst needs to beadded to the FCC unit in a more or less continuous fashion. In general,catalyst addition rates (CAR, usually in tons per day or lbs per barrel)are added in the range from 0.05 to 0.5 lbs of catalyst per barrel ofoil processed. Another way to characterize this is by saying that theCAR varies from ˜0.5% to ˜5% of the total inventory. In general thesevalues are a consequence of many parameters that are related to both theunit and the oil feed properties. Because of this continuous (at leastin principle) catalyst addition, catalyst losses and catalystwithdrawals, the actual catalyst working at any given time in an FCCunit is intrinsically a blend of catalysts with different ages. Eachunit has its own characteristics and for those versed in the Art, theterm Equilibrum Catalyst or ECAT represents the physical blend of theresulting catalyst that was formed in the FCC unit by controllingadditions around a set of “Equilibrium Properties” that make theoperation stable within an operating window which may or may not vary intime. This will become an important aspect of this invention as the“aging” process results in changes in the physical, chemical andcatalytic properties of the original catalyst. Thus “equilibriumcatalyst” or ECAT is by definition a used catalyst and contains at leastsome catalyst added to the original charge more or less continuouslyover the tenure of its use. Thus an “ECAT additive” as used herein is amaterial added periodically during the tenure of use of the ECAT.Equilibrium catalyst also often includes a significant portion of fineswhich are collected by the user over time, in a third stage separator,an electrostatic collector or other fines capturing device. The userwill have added these collected fines to the ECAT before sending theECAT to the processor. I intend for the definition of equilibriumcatalyst to include ECATs that include such recycled fines. The term“recycled fines” includes such collected fines added to or mixed with anECAT.

The chemical nature of FCC catalysts is well known to those versed inthe Art. These catalysts generally contain zeolite Y in one or severalforms (RE-Y, USY, RE-USY, CREY, etc) as the main source of activity andselectivity. Some other zeolites like ZSM-5 can be added to change theselectivities both as an intrinsic part of the catalyst or as a separateadditive particle. Aluminas or Silica Aluminas of different propertiesare sometimes added to increase the activity for conversion of heavymolecules (bottoms upgrading). Clay is used as a filler that assistswith the catalyst's chemical and physical properties. A binder,generally a low molecular weight oligomer of Silica (Silica Sol), orAluminum Chlohydrol (Alumina Sol) is added to the mixture which is spraydried to form the particles that are shipped for usage, with or withouta further post-treatment to adjust the chemical composition and set thedesired selectivities. Another type of commercially available FCCcatalysts, the so called “In-Situ” technology, takes preformedspray-dried particles of Kaolin clay and other materials like Silica andaluminas and chemically treats them to form Zeolite Y based FCCcatalysts.

It is accepted by experts in the field that FCC catalysts suffer bothhydrothermal and metal deactivation. The steam sources that causehydrothermal deactivation are from both the process and consequence ofcombustion. The metals that cause catalyst deactivation originate in thefeedstock and accumulate in the catalyst. In general, steam and hightemperatures result in destruction of the zeolite. This effect isaccelerated by the presence of vanadium especially when it is present inits V⁺⁵ state. These phenomena also result in a noticeable loss ofsurface area on the matrix. Thus, catalysts used with lighter feedswhich usually contain less contaminant metals (Ni, V, Fe) aredeactivated less severely than those in which the metals in the feed aresubstantially higher, thus keeping a larger fraction of the originalactivity and selectivity. CAR is usually higher for units with highmetals in the feedstock.

As a catalyst particle ages within an FCC unit, it tends to pick upmetals such as vanadium and nickel and to lose its crystallinity, botheffects inversely increasing density even though the dimensions of theparticle may remain constant. Density of the FCC ECAT is typicallymeasured in terms of Apparent Bulk Density (ABD), usually in grams percc. Iron poisoning is known to have changed catalyst morphology,resulting also in an increase in density. Because the efficiency ofcyclones is dependant on the momentum (e.g. mass) of the particles,large (diameter), heavy particles (those having high ABD) have a muchbetter retention than smaller ones. As a consequence, large, oldparticles are primarily removed from the FCC unit via catalystwithdrawals as their retention due to cyclone efficiencies increases asa function of time.

It is generally accepted that nickel is deposited on the outside shellof FCC catalyst particles and it is more or less immobile from particleto particle. However, although vanadium is also deposited in the outsideof the particles, it is well established that it migrates intraparticleand from particle to particle. Conditions of high oxidation state andsteam accelerate vanadium mobility and thus zeolite destruction. Nickeldoes not deactivate the catalyst and some even propose that it somewhatdelays the activity of Vanadium. Nickel's most important effect is thatit is a dehydrogenation catalyst which increases undesirable reactionsresulting in high hydrogen and coke yields (V also has dehydrogenationactivity. An accepted correlation is that V is ˜¼ as active as Ni fordehydrogenation). At constant particle size, Ni on a particle is thus agood measure of its relative age. Depending on the mobility of theVanadium, the profile for vanadium is flatter relative to time as eventhe freshest part of the inventory contains a substantial amount ofVanadium.

Thus the nature of ECAT's is such that every unit has different ECATproperties. In general, units processing light feedstocks result in ECATwith low Ni, Vanadium and other contaminants. Also because of the lowcoking tendency of the feedstock combined with low ECAT dehydrogenationactivity (e.g. coke and H₂ yield), low metal ECAT are generally veryactive as they have retained a substantial percentage of the freshsurface area. On the contrary, units processing heavy or highlycontaminated feedstocks with high levels of Ni, V and other contaminantsresult in ECAT with high levels of these undesired metals. These metalsresult in severe catalyst deactivation and high dehydrogenation activity(e.g. coke and H₂ yield) which make the catalyst make up requirementsmuch higher. Because of the heavy feedstock's higher coking tendencycombined with the fresh catalyst activity and coke selectivity, thefresh CAR for these heavy feedstock FCC units can become limited by thecoke yield. In this case, addition of a catalyst with low activity (e.g.ECAT) can be used to improve the coke selectivity of the system. In somecases, operators use this type of ECAT “flushing” to maintain catalystscost within a budget. In practice, the ECAT that is withdrawn from unitsthat process feedstocks with low metals (“high quality, low metals, highactivity ECAT”) is injected into units that process feedstocks withhigher metals in order to control metal levels on ECAT or to manage theproper activity and selectivity levels. These heavy feedstock unitsresult in ECATS with much lower activity and higher metals than the lowmetal operation. The consequence of this addition is that metals in thehigh metal operation are “diluted” relative to an operation in whichonly fresh catalyst is added. The optimal conditions are unit dependentand in some cases it is not economical to add the ECAT from certainunits to other units that process feed with higher metals.

Thus, ECAT with relatively low metals has economic value for someoperations. Although exact values may vary, ECAT with Nickel andVanadium levels less than 1500 ppm each and with total levels (Ni+V)preferably less than 2500 ppm are considered valuable. ECAT with highermetals is usually sent to cement kilns and or sent for disposal, usuallyat a substantial cost to the operation. In general high quality ECAT issold for reuse at $600-1000/MT depending on ECAT composition and marketconditions. Refiners sell high quality ECAT to ECAT brokers at pricesvarying from $100-$600/MT. When ECAT is sent for disposal or use incement kilns, ECAT has usually zero or negative value to pay forassociated transportation and disposal costs. Blending of low value ECATwith high quality ECAT is practiced to meet a set of specifications.

A good illustration of vanadium and nickel distribution in ECAT is foundin the paper of R. Pimenta, A. R, Quinones, and P. Imhof titled “FCCTesting Philosophy” published privately by Akzo Nobel InternationalSymposium, Noordwijk, The Netherlands, 1998. showing analyses ofequilibrium catalyst fractionated by using liquids of differentdensities, without attempting to segregate even quartiles by weight.Table 2 from that paper is reproduced in part below as Table I:

TABLE I Fraction ECAT Lightest Med-Light Med-heavy Heavy Wt % of Sample100% 21% 22% 20% 37% Surf Area, Mg²/g 138 183 166 141 106 MiPore Area,Mg²/g 112 138 128 109 82 Nickel, ppm 2,178 715 1,007 1,777 3,721Vanadium, ppm 5,080 3,511 4,271 5,031 6,264 Ni/V, wt/wt 0.4287 0.20360.2358 0.3532 0.5940

As illustrated above and further explained in the above cited paper andelsewhere in the literature, the nickel and vanadium contents areimportant determinants of the weight ranking. Particles having higher Vand Ni contents are older and less active than the others. The mobilityof the vanadium is reflected in the Ni/V ratio, and clearly trendsupward as the particles become older.

In the prior art, researchers have focused on and patented methodologiesto recover the low metal part of the ECAT. The so called MAGNACATprocess used magnetic separation. Others have tried to selectivelyremove the metal contaminants.

In U.S. Pat. No. 5,393,412, Hettinger et al employ an attriting processto generate smaller particulates while also removing undesired metals onthe surfaces of the catalyst; they can combine this approach withcertain magnetic and size classifier techniques. Goolsby et al in U.S.Pat. No. 7,431,826 combine a magnetic separation step with gravityseparation; the magnetic separation step may also be accompanied by theuse of a filter screen to remove larger particles.

Air cyclone separations are used to adjust the particle size of freshcatalysts to make them conform with FCC unit requirements to avoidexcessive losses. This application is clearly different than the presentinvention in that it is utilized only on homogenous fresh catalystsystems.

Magnetic systems are expensive to install, to operate, and to maintain.The art is still in need of a reliable, economic method of recycling asmuch ECAT as is reasonably possible.

SUMMARY OF THE INVENTION

The subject invention employs the physical properties of fractions ofthe ECAT to obtain fractions having at least one improved catalyticproperty. By using cyclonic or other density separation methodology,such as air classifying, on narrow ECAT size fractions, separation intotwo or more fractions having different values, properties or usefulnesswill be achieved. The narrow size fractions are conveniently obtained bysieving, preferably with vibration.

A different embodiment will be applied when the catalyst is a mixture ofparticles with different physical properties irrespective of whether ornot it has been in an FCC unit already (e.g. ECAT or fresh catalystsmade from mixtures of two or more components). For example, samplescontaining inactive clays may have two fractions with very differentdensities. This may also occur when additives such as ZSM-5 (for Octaneor Propylene or other LPG olefin improvement) or Sox reduction (forenvironmental control of sulfur dioxide emissions), or other additivesare added. Not only do the fresh catalysts have different properties,the aging process is very different for each of them. For example, thestability of the ZSM-5 zeolite structure is understood to besubstantially higher than that of Y zeolite. It is possible then that acyclonic or other separation may be used to separate such blends at anygiven point in the aging process. The optimal separation will depend inmany factors.

Embodiments of the invention may become increasingly important as theapplication of high C3=(propylene) systems which contain mixtures of FCCcatalysts and large amounts of ZSM-5 based additives become limited, asfew FCC units can tolerate the ECAT from such systems. An embodiment ofthe invention would have a process that could separate or enrich thefractions into two systems, each of higher value than the originalblend.

An embodiment of this invention has as primary objective to separateuseful fractions from ECAT sources which have limited applicationbecause the average metal level is too high. For example, a catalystthat is considered a waste, and that currently is disposed to landfillsor used in cement kilns can be used as a source for processing by theinvention. Metal concentrations of Ni and V above 2000 ppm each and 3000ppm combined are considered to indicate that the ECAT has limited valueas resalable ECAT for use in FCC units. However, an embodiment of theinvention will separate such portions of this ECAT for further use.

An embodiment of this invention will use a separation technology thatseparates the “newer,” low metal, high surface area fraction from the“older,” high metal, low surface area, low value fraction.

In another embodiment of this invention, an ECAT that contains additivesthat are used to change the selectivities of the base catalysts may beseparated so that certain resulting fractions are enriched in theadditive and other resulting fractions are depleted in the additive. Forexample, an ECAT containing 25% of a ZSM-5 additive and 75% of the basecatalysts may be separated so that the resulting fractions contain:

-   -   A ZSM-5 enriched fraction with greater than 25% ZSM-5 additive        and less than 75% of the base FCC catalysts    -   A ZSM-5 depleted fraction with less than 25% ZSM-5 additive and        greater than 75% of the base catalysts

The ZSM-5 enriched fraction is characterized by having a greaterselectivity toward light olefins like propylene and butylenes relativeto the starting material. This fraction can be used in FCC units thatvalue these light olefins and or improve octane for which ZSM-5 is used.The ZSM-5 depleted fraction is characterized by having greaterselectivity toward gasoline and other liquid yields. This fraction canbe used to target units that do not value light olefins as much asgasoline or other liquid products.

I have found that highly useful fractions of ECAT may be obtained byfirst separating the ECAT into fractions by size and then furtherfractionating selected size fractions by density. I am able to use airclassifiers and cyclonic separation very effectively to segregate bydensity after the ECAT has been fractionated by size. The efficiency offractionation by density is enhanced by using fractions of narrow sizedistribution, generally regardless of the type of ECAT, its age, or itscomposition. Efficiency of my system is enhanced also in many instancesby first removing a fines fraction by an air separation device beforesubjecting the remainder to further size fractionation by sieving. Insome instances also, the largest particle size fraction isadvantageously removed by an air separation device before passing theremainder to a sieving step. By an air separation device, I mean toinclude a standard commercial air classifier or a standard commercialair cyclone, both of which types of machines are well known to the art.

Definition—I use the term “air classifier” to mean either a standardindustrial air classifier such as the ACS-005™ made by RSG, Inc. orsimilar devices or an industrial air cyclone also made by RSG, Inc, or acombination of both. The air classifier I use has a limited ability torecognize density as a factor in fractionation. I have found that itsability to fractionate using density as a criterion, and its densitydependency, are enhanced by introducing a particulate ECAT or fresh FCCcatalyst that has already been fractionated by size.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified process flowsheet to show apparatus to separatecatalyst

FIG. 2 is a plot graph demonstrating the PSD of fines recovered withkinetic screening

FIG. 3 is a plot graph showing Ni Content

FIG. 4 is a plot graph showing V Content

FIG. 5 is a plot graph showing the BET surface area

FIG. 6 is a plot graph showing P2O5 content

DETAILED DESCRIPTION OF THE INVENTION

As indicated above, it is known in the art that high metal content inECAT is generally correlated to high coke formation, leading to lowconversion rates, and conversely particles containing low concentrationof metals, particularly nickel and vanadium, can be expected to continueto perform at acceptable rates as they get older. Example 1demonstrates, however, that particle size is also a factor. Indeed,Example 1 will demonstrate that when the low metal content resides inlarge particles, conversion can be low enough to suggest removal of thelarge particles.

Example 1 Particle Size Effect

An ECAT from a working FCC unit was obtained and had the followingproperties based on an average of 4 samples collected (to minimizevariations due to measurements)

TABLE 2 Conversion, wt % 73.7 Vanadium, wt % 71.2 CPF¹ 1.4 Al2O3, wt %51.2 GPF² 2.0 C, wt % 0.03 SA, Mg²/g 142.4 0-20, wt % 0.0 MSA, Mg²/g 850-40, wt % 1.5 Na, Wt % 0.2 0-80, wt % 43.2 RE, wt % 1.64 APS, μm 85.6Nickel, ppm 226 ¹Coke factor ²Gas factor

The definitions of conversion, CPF (Coke factor) and GPF (gas factor)are known to those experts in the Art.

This sample was then subjected to a separation by particle size using aSWECO MX-48™ Vibro-Energy Round Separator equipped with screensaccording to the desired particle size cut. This commercially availablemachine utilizes both vibration and tilting to assist in the sievingprocess. In a preferred embodiment, the screens may be equipped withspecial equipment to avoid plugging of the screens with fines. Swecoprovides such equipment either as a removable screen with large holes inwhich balls are or inclusive to the screens. The vibrational frequencies(horizontal and vertical) of the equipment may be optimized by trial anderror as each ECAT has unique properties.

In this example, we used a single screen system that was changed oncethe whole product was passed through. We started with the largestfraction since this is the easiest to screen at a fast rate. The nextsmaller screen was then installed and the material that passed throughthe screen was fed. This was repeated with all the available screens. Wehave also carried out experiments with multiple screens at once and theyalso work and may be used in my invention. The kinetic energy applied tothe sieves should be adjusted in order to minimize excessive “jumping”of the particles which tends to generate dust. A cover on the system ispreferred. Some of the most important properties of the fractions arepresented on the following Table 3.

TABLE 3 Sample SA, Na, RE, Ni, V, Al2O3, APS, ID Mg²/g wt % wt % ppm ppmwt % μm Fraction 1 144 0.23 1.70 519 786 50.3 49 Fraction 2 128 0.241.70 413 825 50.4 64 Fraction 3 137 0.23 1.80 360 853 50.2 89 Fraction 4134 0.26 1.80 274 783 51.0 116 Fraction 5 137 0.25 1.80 274 799 51.4 152

In order to demonstrate the usefulness of the invention, Fraction 5 wassent for testing and was compared with the original sample. Below, inTable 4, are the results of the catalytic testing.

TABLE 4 Sample ID Conversion, wt % CPF GPF Fraction 5 71.8 1.75 1.69 2week Average¹ 73.7 1.4 2.0 Change −1.9 0.4 −0.31 ¹The 2 week average isthe plant record for the ECAT sample as a whole.

For those versed in the Art, it is clear that the yields of the Fraction5 with a large particle size distribution are detrimental to the yieldsof the blend. In other words, removing Fraction 5, having the largestparticle size distribution, from the original sample would yield aproduct with improved conversion and improved Coke Factor. This findingis completely contrary to the generally accepted principle that lownickel and vanadium contents will result in lower coke.

My invention therefore includes a process of making an improved ECAT byremoving particles larger than 90 microns. If desired, the cut-off couldbe at 100 microns, 110 microns, or 120 microns or any other cutoff above90. My invention includes a composition comprising ECAT of particlesless than 105 microns and no more than 5_% particles larger than 105microns; also my invention includes ECAT consisting essentially of nomore than 5% by weight particles more than 105 microns and the balanceparticles less than 105 microns.

Example 2 Fines and Fractionation

An ECAT from a working FCC unit was obtained and found to have thefollowing particle size distribution (PSD), as shown in Table 5:

TABLE 5 % Passing Size, μm 10 23.38 20 35.82 30 46.38 40 55.00 50 62.5260 69.57 70 76.94 80 85.47 90 97.59 95 107.8

Fines content above 2 wt % in the less then 20 microns range and 15% inthe range less than 40 microns are considered high for ECAT purposes.Clearly this ECAT contained excessive fines which are undesirable in theFCC unit but also interfere with the separation in the kinetic screeningprocess. Accordingly, an original sample was then subjected to aseparation using a SWECO MX-48 Vibro-Energy™ Round Separator identicalto that used to obtain the PSD shown in Table 5. However, even afterseveral adjustments on the kinetic energy input (vibrational energy onthe horizontal and vertical axis) were tried, the rates of theseparation were much slower than those of the procedure used to obtainthe result shown in Table 3. We also noticed plugging of the screens.

In order to achieve a better separation by particle size in the presenceof a lot of fines, the sample was introduced to an ACS-005™ airclassifier made by RSG, Inc. of Sylacauga, Ala. The feed was injectedvia a screw feeder at a measured rate of about 700 lbs/hour. The motorwas run at several conditions but we opted for 1100 rpm as a reasonablerate to separate the finest and lightest 35% of the sample. The particlesize of the fractions is shown on Table 6. After removal of the fines,the coarser material was then passed to the kinetic separator (the SWECOMX-48™ vibrating sieve system described above) with much improved rates.Rates of greater than 500 lbs/hr were achieved with good separation forthe equipment used. These rates are not feasible with the fines present.

TABLE 6 Starting ECAT with Fines Material Removed Fines Removed 100% 65%35% % Passing Size, μm Size, μm Size, μm 10 23.38 49.99 3.33 20 35.8261.70 4.90 30 46.38 70.04 6.78 40 55.00 77.40 9.14 50 62.52 84.55 12.2660 69.57 92.23 15.95 70 76.94 101.1 1.25 80 85.47 112.9 25.90 90 97.59132.8 36.52 95 107.8 154.1 49.00

Example 3 Density/Particle Size Separation

The effectiveness of the air classifier to distinguished particles ofdifferent densities is improved by injecting particles with a narrowPSD. The ECAT in this example is known to contain at least threecomponents: a high surface area FCC base catalyst (tracked by Rare Earthcontent), a ZSM-5 additive for propylene production tracked byPhosphorus content, and a low surface area component without rare earthand phosphorus. The amount of each of the components is not knownexactly. Pure ZSM-5 additives usually have approximately 10 wt % P2O5.One must remember that it is likely that the three components differ inparticle size distribution. Here, the coarser/heavier material fromExample 2 was fractionated in the kinetic separator by using screenswith cuts at approximately 120, 85, 60, 50 and 40 microns.

The following Table 7 shows all the separations that were done on theair classifier in each of the different fractions collected from thekinetic separator:

TABLE 7 Experimental Conditions Average Particle Surface Area EXPERI-Fraction feed Size, microns m2/g MENT Fed rpm rate Light Heavy LightHeavy 8 45 to 55¹ 1100 432 9 Heavy 8² 750 344 53 147 11 65 to 85³ 750769 12 Heavy 11 750 523 79 148 13 Light 11 750 434 78 154 14 85 to 120⁴750 472 15 14 Heavy 750 327 102 157 16 14 Light 750 310 99 158 17 120plus⁵ 750 268 148 155 ^(1,3,4,5)the units are microns; the nominalscreen limits are approximate - light scattering techniques were used todetermine the fraction particle sizes. ²The heavy fraction obtained inexperiment 8 was fed.

As a matter of example, Experiment 11 is the fraction collected byscreening the sample used for Table 6 with the screens of nominally 85and 65 microns. This was fed to the air classifier identified above witha feed rate of 769 lbs/hr at a rotor speed of 750 rpm and air blowerfrequency of 60 Hz. The product denominated Light 11 was 39% and theproduct denominated Heavy 11 was 61%. The Heavy/Coarse (Heavy 11, 61%)material was then fed with similar conditions with exception of areduction in feed rate to 523 lbs/hr in Experiment 12. The fractionsrecovered were 45% Light 12 and 55% Heavy 12. Sample Heavy 12represented the heaviest and or largest particles sieved with thescreens between 85 and 60 microns.

The Light 11 product was then also processed again in the air classifierwith a feed rate of 434 lbs/hr in Experiment 13. In this case, theproduct recoveries were 47% for the Light 13 and 53% for theheavy/coarse material Heavy 13. The surface area analysis of the Light13 and Heavy 12 samples, both from the same cut from the kineticseparator substantiate a lighter fraction given the higher surface area.Both the light and heavy fractions obtained may be further fractionated.Generally, they may first be fractionated by size with the kinetic sievedevice and then further utilizing density differences in the airclassifier. Further data has shown that a much higher rotor speed wouldlead into a better separation. This will be the subject of anotherexample.

Three of the samples above were also submitted for chemical analysis,with the results shown in Table 8.

TABLE 8 SiO2, Al2O3, TiO2, Na2O, Fe2O3, La2O3, V, Ni, Zn, P2O5, SampleWt % Wt % Wt % Wt % Wt % Wt % ppm Ppm Ppm Wt % Heavy 9 54.9 39.8 1.390.27 0.85 1.09 292 406 86 2.74 Heavy 17 55.1 39.8 1.28 0.29 0.75 0.53210 183 51 4.37 Heavy 12 54.8 40.3 1.39 0.25 0.86 0.92 294 311 76 2.63

Table 8 has some useful information sheds light into the components ofeach fraction.

Fraction “Heavy 17” clearly has a much higher ZSM-5 additive contentthan any of the other two fractions. This indicates a concentration ofZSM-5 approaching 45%. This is also reflected on the much lower La2O3content which is associated with the base catalyst. The TiO2 and Fe2O3are lower thus suggesting also a lower content of such inactivecomponent (clay that usually contains both of those contaminants). Soeven though the total base zeolite is lower, the clay is also lower.Taking into consideration that ZSM-5 is a very stable structure thatsuffers very little loss of crystalinity upon deactivation, we canexplain the higher surface area of this Heavy fraction. Heavy 17 is aclear candidate for reuse in the FCC unit.

Example 4 Recovery of Valuable Product from Air Classified Fines

The use of Air Classification for removal of undesired particles,usually trying to control the 0-20 microns range is known to experts inthe Art to correct for batches of catalysts that contain an excessiveamount of fines. Recently, some refiners have started to set aspecification on the 20-40 micron range as these particles tend to belost preferentially from the FCC unit. Some unit designs are capable ofrunning even with very few particles in that range (less than 3 to 5 wt% is considered low for many units) but some of these units can functionnormally at least from a physical point of view. Some catalystmanufacturers have then opted for Air Classification of their productsin order to meet the new specifications. However, it is also known that,besides removing the undesired particles, air classification results ina substantial loss of desirable products. We have also indicated thesieving of fines from an ECAT (or fresh catalyst) can be achieved butusually at slow rate. Also we have mentioned that screens tend to plugthus making the process inefficient unless a lot of machines are used inparallel. In this example, we show that by using a combination of AirClassification followed by screening of the fines under the rightconditions, it is possible to dramatically reduce the amount of lossescaused by the use of the Air Classifier alone. Because the ECAT productis of limited value relative to the costs to segregate effectively, theextra recovery of valuable samples is enough to convert this processfrom negative added value to positive added value.

In this example, the air classifier was run at 1500 RPM with a feed rateof 512 lbs/hr yielding 26% yield of fines and 74% of coarser product.The product in this case was a spray dried particle with a homogeneouscomposition across the particle size. Table 9 shows the resultsobtained.

TABLE 9 Original Coarse Fines SIZE, μm 100% 74% 26% 0 to 20 2 0 5 0 to40 22 6 64 0 to 80 66 54 93 0 to 105 81 78 96 0 to 125 89 89 97 0 to 15095 0 98 APS 62 78 35

As can be seen on Table 9, the fines contain 26% of material that is0-40 microns with only 5% being 0-20%. This means that in order toreduce the 0-40 micron content by 16 wt %, we had to reject 26% of theinitial sample. In order to improve the yield, this material wasprocessed in the kinetic separator (sieves) with a 45 micron screen butadjusted with a feed rate of less than 200 lbs per hour and a higherdegree of vibration (as per the manufacturer manual) optimized tominimize plugging of the screens even at the expense of a less thanoptimal separation. In other words, it is more or less unavoidable thatsome particles that have the potential to be screened are left in thefinal product in order to minimize the chance of plugging the screens.In this example, we were able to process the fine material and recovertwo fractions with the PSD shown on the figure below. Of the total 26%of the original sample, 14% of the sample was rejected and only 18% ofthe particles were measured to be below 40 microns (probably due toimperfections on the screens). Thus, with the combination of bothtechniques, in order to reduce the 0-40 micron by 14% (from 22% to 8%)we only lost a total 14% for an almost perfect separation.

This type of separation was also done on ECAT's with very similarresults. Thus a combination of both techniques is not only commerciallyfeasble but it practically minimizes the “waste” of good product thusenhancing the feasibility of this application.

Example 5 Multiple Passing Through a Classifier

The same ECAT from example 2 is used as starting material. However,instead of pre-screening the fines at a very high rate, a sharper cutwas attempted by running the air classifier at a higher speed (2000 RPM)while also reducing the feed rate.

Table 10 shows all the separations that were done on the original sample(Experiment 13A) and on different fractions (13A Coarse/Heavy and 13AFines/Light). For completeness, the labels on the results indicate thatthe separation includes not only the particle size separation but alsodensity effects.

Average Particle Size, Surface Area Experimental Conditions microns m2/gFeed Light/ Heavy/ Light/ Heavy/ Light/ Heavy/ EXPERIMENT Feed RPM rateFines Coarse Fines Coarse Fines Coarse 13A ECAT 2000 356 35% 65% 40 84149 159 14A 13A 1200 459 62% 38% 76 105 157 160 Coarse 15A 13A 2200 35464% 35% 31 62 145 153 FinesAll the samples (with the exception of the fines from the first passthrough the screener) were submitted for chemical analysis. The resultsare shown on Table 11.

TABLE 11 APS, μm Ni ppm V ppm P2O5 Wt % 70 334 251 3.0 84 261 238 3.1106 211 211 3.2 76 286 239 2.8 62 341 255 3.0 31 433 265 2.7

In order to see if further separation was still possible, the fractionsfrom Experiment 14A were sieved. The fines/lighter fraction was sievedwith a 75 micron sieve while the coarse/heavier sample was sieved with a106 micron sieve. The following results were obtained:

Cut BET, Ni V P2O5 Estimated EXPERIMENT Feed Point, □m % SA ppm ppm Wt %APS, □m 14A Fines/Light 75− 62% 154 343 256 2.8 60 14A Fines/Light 75+38% 163 225 232 3.1 85 14A Coarse/Heavy 106− 63% 159 258 235 2.7 90 14ACoarse/Heavy 106+ 37% 159 152 191 4.6 120

FIGS. 3, 4, 5, and 6 summarize the results in a graphical waydemonstrating the dependency of the metals Ni, V, known poisons, BETsurface area, a measurement of crystallinity in these materials, andP2O5, a measurement of the amount of ZSM-5 in the sample.

Referring now to FIG. 1, which is a simplified process flowsheet, auseful apparatus for practicing the invention is seen to comprise an airclassifier 1, an air cyclone 2, a dust collector 3, and a blower notshown. These components are well known in the art. The blower draws airthrough the entire system, beginning at ECAT source 4 which is a ductthrough which the ECAT particles are drawn into air classifier 1. Boththe air classifier 1 and the cyclone 2 are affected by rotation speed,which is adjustable. The air classifier 1 includes an interior rotorwhich affects the separation of particles. Generally, the larger,heavier particles fall to the bottom of air classifier 1 and the lighterones proceed to the cyclone 2. The cyclone 2 operates only on kineticforces, but also makes a two-part separation, the larger, heavierparticles falling to the bottom and the lighter ones being drawn intothe dust collector 3. Dust collector 3 is used primarily forenvironmental purposes; the particles it collects are generally quitesmall. The operator may collect the larger, heavier particles from thebottom of air classifier 1, while the particles in the bottom of cyclone2 will generally be lighter and smaller. As indicated above, I refer tothis entire assembly as an air classifier.

In one useful practice, a selected fraction having a width range nogreater than 30 microns is collected from a set of sieves not shown andfed to the air classifier 1 through source 4, where it is separated asindicated above, the lighter smaller particles being sent to the cyclonefor further separation.

Any sieving system effective to sort ECAT by size may be used in myinvention. Vibrating and tilting techniques known in the art may be usedto enhance the accuracy and speed of the process. Any air classifier orair classifier system effective to sort particulate ECAT may be used inmy invention; as indicated above, the ability of the air classifier torecognize density as a criterion for sorting is enhanced by feedingnarrow width fractions to it.

The operator has considerable discretion in the choice and number of andtype of sieves, and whether to employ enhancements such as vibrators,but for my invention it is necessary that at least one fraction beobtained having a size range no wider than 30 microns, more preferably20 microns, and most preferably no more than 10 microns.

Thus, it is seen that my invention includes a method of making acatalyst composition having at least one improved catalytic propertyfrom a particulate equilibrium catalyst comprising (a) fractionatingsaid equilibrium catalyst by size, (b) recovering at least oneparticulate size fraction from step (a) comprising at least 80%particles within a size range having limits no greater than 30 micronsapart, (c) further fractionating said at least one particulate sizefraction in an air classifier, to obtain at least two subfractions, and(d) recovering at least one subfraction having at least one improvedcatalytic property.

My invention also includes a method of separating from an equilibriumcatalyst containing recycled fines a fraction of said equilibriumcatalyst having at least one catalytic property superior to saidequilibrium catalyst comprising (a) removing from said particulateequilibrium catalyst at least 90% by weight of all particulates lessthan 20 microns in dimension, thereby obtaining a portion of equilibriumcatalyst depleted in fines, (b) fractionating said portion ofequilibrium catalyst depleted in fines to obtain at least one fractionthereof within a size range having limits no greater than 30 micronsapart, and (c) further fractionating said at least one fractionutilizing density as at least one criterion, to obtain at least twosubfractions thereof, and (d) recovering at least one subfraction fromstep (c) having at least one catalytic property superior to saidequilibrium catalyst.

In addition, my invention includes a method of improving the catalyticproperties of a particulate equilibrium catalyst comprising (a)optionally discarding at least 50% of particles therein of a size lessthan 20 microns (b) fractionating the remaining equilibrium catalyst bysize, (c)_recovering at least one particulate size fraction from step(b) comprising at least 80% particles within a size range having limitsno greater than 30 microns apart, (d) further fractionating said atleast one particulate size fraction recovered in step_(c) utilizingdensity as at least one fractionation criterion, to obtain at least twosubfractions, and (e) discarding at least one subfraction from step (c)having at least one catalytic property detrimental to said equilibriumcatalyst.

Also, my invention includes a method of making an equilibrium catalysthaving at least one improved catalytic property comprising removing fromsaid equilibrium catalyst an amount of particles larger than 90 micronseffective to improve said at least one catalytic property.

And, my invention includes a particulate equilibrium catalyst includingno more than 5% by weight particles larger than 105 microns.

It also includes a method of modifying a fresh catalytic crackingcatalyst or an FCC additive therefor to improve at least one catalyticproperty thereof comprising removing from said fresh catalytic crackingcatalyst or additive therefor at least some particles larger than 90microns.

The invention also includes a particulate fresh catalytic crackingcatalyst including no more than 5% by weight particles larger than 105microns.

I claim:
 1. A particulate cracking catalyst including particles havingfrom 20-40 microns and no more than 5% by weight particles larger than105 microns and wherein at least 90% by weight of all particulates less20 microns have been removed, wherein the catalyst is used in a fluidcatalytic cracking petroleum refining process in order to refinepetroleum.